recensies: I always have plenty of fresh AA batteries around but never C or D because there are only a limited number of items that require that size anymore. But, I do have 2 Mag lights that use 3 D cells and with this little converter I do not have to have a bunch of different sizes lying around. Just pop in a AA cell into the unit and the flashlight is working like a charm. Just the handy thing to have a few of when they are needed.